Upstream dependencies

[Keno]

Keeping track of all the things I needed to fix upstream, so I don't forget anything:

Zygote

• More stuff... (fill me in)

Flux

• More stuff... (fill me in)

Julia

• Backport CFG simplification pass from XLA backend JuliaLang/julia#29544
• RFC: Allow structural recursion without triggering edge cycle limiting JuliaLang/julia#29294
• Extend code_typed to be able to debug constant prop JuliaLang/julia#29261

Done

Zygote

• Delete unused type parameters FluxML/Zygote.jl#25

Flux

• Non-isbits arguments passed to CUDAnative FluxML/Flux.jl#353

ForwardDiff

• Remove need for valtype of Dual to be <: Real JuliaDiff/ForwardDiff.jl#216

Julia

• Fix inling of _apply(_apply, ...) JuliaLang/julia#29622
• Make broadcast recursion in flatten structural JuliaLang/julia#29816